Acoustic modem



FIG. 1 is a front, top and right side perspective view of an acoustic modem showing my new design;

FIG. 2 is a top plan view;

FIG. 3 is a front elevational view;

FIG. 4 is a bottom plan view;

FIG. 5 is a left side elevational view; and

FIG. 6 is a right side elevational view. 

The ornamental design for an acoustic modem, substantially as shown. 